Ladder levelling means



Filed Jan. 6, 1954 IN V EN TOR. JOHN A. 5/14 CAP BY @wy. ATTOP/VEK United States This invention relates to ladders and has particular relation to supporting, self-adjusting legs for such ladders. The conventional ladder has several grave disadvantages which sometimes render it quite dangerous in use and, in any event, it frequently requires blocking and the like to properly support the ladder.

The disadvantages of the conventional ladder may be divided into at least two classifications. One is that it may be necessary to use the ladder on sloping or rough ground, in which case it may be necessary to block up one leg of the ladder. which, of course, entails loss of time in finding suitable blocking materials and also, usually, the difference in co-efiicient friction of surfaces on which the legs of the ladder rest may beconducive to dislodgment of one leg of the ladder before the other, or toppling of the supporting blocks, or unequal sinking of the two supporting surfaces.

Perhaps an even worse difficulty of the conventional ladder is that which occurs when supporting surfaces are unequal in supporting ability and, on application of a persons weight on the ladder, sinking of the ladder occurs. Under these conditions, all or substantially all the weight of the person is supported on one leg of the ladder and only the friction of the upper end of the ladder against a wall or the like keeps the ladder in position with the result that any sliding of the upper end of the ladder in transverse direction, or breakage of the ladder, may result in a serious accident.

It is one of the main objects of my invention to provide an extension for ladder legs which will automatically adjust to compensate for any difference in the level of the supporting surface such as on rough ground or on stairways or the like.

Another important object of my invention is to provide a device of the above character in which the supporting legs are inter-connected so that supporting surfaces of unequal supporting ability, and more rapid failure of one surface in relation to the other, will automatically cause the extensions to adjust to this difiiculty even though a person is on the ladder.

A still further object of the invention is to provide a device of the above character in which a locking means is supplied for each ladder leg extension so that a greater pressure on one extension will permit a retraction of that extension and extension of the other support, but which will prevent movement of the extensible members in a direction counter to the pressure.

A still further object of my invention is to provide means for extending of one or the other leg of the member and retraction of the remaining leg until the pressure on the two legs is substantially equalized.

A still further object of my invention is to provide a relatively inexpensive and very reliable compensating means of the above character.

Other and further features and objects of the invention will be more apparent to those skilled in the art upon a consideration of the accompanying drawings and following specifications, wherein is disclosed a single exatent ice emplary embodiment of the invention, with the understanding, however, that such changes may be made therein as fall within the scope of the appended claims, without departing from the spirit of the invention.

In said drawings:

Figure 1 is a view in elevation of a ladder to which extending legs have been applied according to one embodiment of my invention. appears when in use on a sloping terrain where supports have unequal heights.

Figure 2 is a view in section taken along the line 22 of Figure 1 and illustrating one of the compensating legs shown in Figure 1.

Figure 3 is a view in section taken along the line 3-3 of Figure 2.

Figure 4 is a view in section taken along the line 4-4 of Figure 2.

Referring again to the drawings: .Each leg of the ladder support, constructed according to the present embodiment of my invention, includes a right-hand and left-hand bracket 10 and 11 adapted to be bolted to the lower end of the ladder 12 by means of bolts 13 and right and left-hand slidable members indicated at M and 16 positioned to move vertically within the brackets.

The slidable members or legs 14 and 16 are connected by means of a flexible strap 17, preferably formed of spring steel, so that when the movement of one of the supports, as for instance 14, in an upward direction occurs, the other support 16 is forced downwardly. In

order to give these leg members a firm grip on the ground surface, I have provided pivotally mounted rollers such as shown at 31 which have a portion thereof flattened and grooved. These rollers are preferably mounted with a tight fit to secure a binding action.

Also slidably mounted within the brackets 10 and 11 are a pair of oppositely disposed locking blocks 18 and 19 which are also connected by a flexible strap 21, also of spring steel. It will be noted that the strap 21 is arched over thepreviously mentioned strap 17 to achieve the cooperative association between the leg members and the locking blocks such as I will hereafter describe.

For purposes of clarity, I will now describe in detail the structure of the left-hand bracket assembly, it being understood that the right-hand bracket is similarlyconstructed but in an opposed position. it will be noted that the bracket 11 is hollow and formed to receive, in sideby-side relation, the leg 16 and block 19. The locking block 19 is pivotally engaged to the bracket 11 by a link 22, with the inner end of the link being connected as illustrated at 24 to the bracket 11 and the outer end 27 pivotally secured to the block 19.

Referring to Figure 3, it will be noted that the bracket member 11 also contains a recessed portion 30 which is adapted to receive a coil spring 29 which in turn is positioned to bias downwardly on the locking block 19.

From the foregoing description, it will be apparent that the cooperative action of the brackets, locking blocks and legs will be substantially as follows.

If upward movement of the block 18 occurs, the links 21 will force it into tight engagement with the outer face of the leg 14.

Conversely, if upward movement of the block 19 with respect to the bracket 11 occurs, the links 22 will force this block into engagement with the outer face of the leg 16.

Thus, if the ladder is placed on the ground, the weight of the ladder is sufficient to cause the leg first striking the ground to move upwardly until the other leg is forced down into contact with the ground. When the persons weight is applied to the ladder as in climbing, both leg Patented May 20, 1958 The device is shownas it 3 14 and 16 are forced upwardly and thus the strap 17 presses upwardly against the strap 21 which in turn pulls the blocks 18 and 19 upwardly. The links 23. and 22 are rotated counter-clockwise and clockwise respectively to cause the. friction blocks 13 and 19 to wedge inwardly against the outer faces of the legs 14 and 16.

In this manner, not only does the ladder compensate for inequalities of the supporting surface, but after such compensation is effective, the weight of the person on the ladder locks these legs in place.

Now suppose that the leg 14 begins to sink into the ground as illustrated by the dotted lines at 28. This releases the pressure of strap 17 on strap 21 and causes the blocks 18 and 19 to move downwardly thus freeing legs 14 and 16 for vertical movement. The legs id and 16 and the strap 17 are free to move in an arc until the pressures on both legs are again equal. At that instant, the strap 17 again engages the strap 21 pulling the loclo ing blocks into locking position and thus stabilizing the ladder at its new position. The spring 29 in each bracket assembly assures the instant release of the locking blocks, thus overcoming any residual friction which might otherwise prevent the prompt and automatic adjustment necessary. In this manner, not only will the ladder compensate immediately for any inequality of supporting surface, but also it will adjust automatically while in use for any unequal sinking of the supporting surface by reason of the weight of the user.

Although I have described a specific embodiment of my invention, it is apparent that modifications thereof may be made by those skilled in the art. Such modifications may be made without departing from the spirit and scope of my invention as set forth in the appended claims.

I claim as my invention:

1. In a supporting device for ladders, a pair of opposed brackets, leg members slidably mounted internally of said brackets and being inter-connected by a resilient arched strap member, a second resilient arched strap member positioned above the first strap member and having a pair of normally open spring-loaded locking blocks attached thereto, said locking blocks being slideably mounted internally of said brackets outwardly of said leg members, link means pivotally attached at one end to the inner portion of said brackets and at the opposite end to said blocks whereby pressure of the first mentioned strap against the second mentioned strap will cause the locking blocks to engage the leg members and hold them in fixed relation to the aforementioned brackets.

2. In a device of the type described, a pair of substantially rectangular brackets, means securing said brackets to the inner face of the sides of the ladder, rectangular leg members vertically and slideably mounted in said brackets, locking blocks slideably positioned within said brackets adjacent said leg members, spring means positioned to urge said locking blocks in normally open position, said blocks having a linking means pivotally connected thereto, said linking means being adapted to bridge said leg members, the opposite end thereof being pivotally attached to said bracket, resilient strap means operatively attached to said leg member, a second resilient strap means interconnecting said locking blocks and overlying said first strap means whereby simultaneous upward movement of the leg members will cause upward movement of said locking blocks, thereby locking said legs in relation to said blocks and brackets.

3. In a supporting device for ladders or the like having a pair of brackets fixedly mounted on the inner face of the sides thereof, spring loaded locking means slide ably mounted internally of said brackets, an arched resilient strap adapted to interconnect said locking portions, linking means pivotally connecting said locking portions to said fixed brackets and adapted to cause said locking portions to move in an arcuate path, a pair of legs slideably mounted in said brackets within the path of arcuatc movement of said locking portions, and a second resilient strap means interconnecting said leg members and slide ably positioned in relation to said first strap member, whereby unequal pressure on said leg members will cause said first and second strap members to move longitudinally and slideably in relation to each other and further positioned in nested relation to said first strap, whereas simultaneous equal pressure on both leg members will cause simultaneous equal upward pressure on said first named strap and said locking portions.

References Cited in the file of this patent UNITED STATES PATENTS 

